1. Field of the Invention
This invention relates to a camera which performs correct exposure control by determining whether the subject is against light at the time of measuring the brightness of the subject, and also to a technique of processing image data in cameras.
2. Description of the Related Art
In a scene where the main subject is photographed against light or backlit as when there is a light source, such as the sun, behind the main subject, the shady part of the main subject is photographed, with the result that the main subject collapses in black.
To prevent this, the shady part of the main subject is lighted by the reflected light from a reflecting plate or illuminating light. Alternatively, when a picture is taken, strobe light is caused to emit light, that is, daylight synchronized flash is done.
In making a decision on backlighting, if the area occupied by the main subject is large for the photographic screen, it is easy to make a decision. However, in a photographic scene where the area occupied by the main subject is small, the luminance difference becomes smaller, which can cause a case where it cannot be determined that the subject is against light. To overcome this problem, for example, Jpn. Pat. No. 2934712 has disclosed an exposure control method of additionally providing a focal point detecting section (distance measuring section) to the photometric section for measuring the brightness in the middle of and the periphery of the photographic screen.
In the invention of Jpn. Pat. No. 2934712, the backlit state of the main subject is detected with a distance-measuring sensor. For example, in a photographic scene as shown in FIG. 3, the distance measuring sensor sets only region 33b as the distance measuring range in the area of the photographic screen 34T.
Furthermore, concerning a method of preventing improper exposure in a backlit photographic scene, a related technique has been disclosed in, for example, Jpn. Pat. Appln. KOKOKU Publication No. 7-27151. In this method, a camera capable of measuring the brightness and distance in a plurality of areas on the photographic screen selects one of the areas on the basis of the distance-measuring data. The photometric value in the selected area is compared with the maximum one of the photometric data in the other areas, thereby making a decision on backlighting. When it is determined that the photographic scene at that time is against light, daylight synchronized flash has been done.
Moreover, in a digital camera, when a backlit scene is not subjected to a suitable image process, the resulting image is unnatural and unattractive. For instance, the contour of the main subject deforms due to the spread of light, which makes it difficult to reproduce a natural image.
To overcome this problem, for example, Jpn. Pat. Appln. KOKAI Publication No. 8-107519 or Jpn. Pat. Appln. KOKAI Publication No. 11-32236 has disclosed the technique for analyzing the luminance distribution of the image data obtained by the imaging element by use of a histogram or the like to detect backlighting and changing the image processing method. Those techniques are for balancing the brightness of the main subject with the brightness of the background, making use of the photographed images.